基于纳米动力学分析的钛薄膜力学行为和疲劳性能研究

Nanoscale Dynamic-Mechanical-Analysis Characterization of the Mechanical Behavior and Fatigue Property for Ti Films

摘要:

利用纳米压痕试验研究了不同厚度钛薄膜的力学行为和疲劳性能。在纳米级动态力学分析的基础上，根据储存刚度的变化定量计算了薄膜的疲劳寿命。结果表明，薄膜的疲劳寿命与残余应力有显著的关系。压痕原位扫描图像显示，薄膜出现明显堆积分层，长裂纹从压头中心向压头边缘垂直延伸。而且，压痕周围积累了大量的应力，纳米级动态加载过程产生了高度局域化的塑性变形和应力释放。薄膜内部的残余压应力将抵消部分载荷应力，提高薄膜的疲劳寿命。

Abstract:

The mechanical behavior and the fatigue property of Ti films with different thickness were investigated by nanoindentation test. The fatigue property of the films was quantitatively calculated according to the changes of storage stiffness under the nanoscale dynamic mechanical analysis. The results showed that the fatigue life of the films depends on the residual stress remarkably. In situ scanning images showed the thin film was significantly stacked and layered, and long cracks radiated from the center of the indenter perpendicular to the indenter edge. Additionally, there was a sizable pile up around the indentions which demonstrated that a highly localized plastic deformation and stress release occurred in the process of the nanoscale dynamic loading process. The existence of the internal compressive residual stress will offset part of the load stress to improve the fatigue life of films.